Alisha Davidson
ML&SA Research & Development Coordinator

muskratMuskrats are semi-aquatic mammals commonly spotted by riparians, particularly in the evening. They prefer locations with four to six feet of water and are found in ponds, lakes, and swamps. Muskrats make a valuable contribution to aquatic communities. By harvesting plants for food and den sites, they create open water for ducks, geese, shorebirds, and other wildlife. In addition, a variety of animals—including snakes, turtles, frogs, ducks, and geese—use muskrat lodges and platforms to rest and nest in. Finally, muskrats and their young are a valuable food source to predators such as foxes and eagles.

While a native part of Michigan’s lakes and streams, they can be a nuisance to many riparians. They reproduce quickly (2-3 litters of 6-8 young in a season) and large number can overwhelm shoreline areas. Muskrats use burrows and nests that they build for shelter, and their burrowing activity can cause shoreline erosion and destabilization. In addition, muskrats are among the few animals that regularly defecate in water, and their droppings can cause a flu like infection, which old-time trappers referred to as “beaver fever.” Finally, more than one riparian has come down to their dock on an evening, expecting to go for a sunset cruise only to find the boat won’t start. Upon inspection, it turns out the various parts of the wiring have been chewed through even on boats that are on a hoist and completely out of the water. Muskrats have even been responsible for sinking boats after chewing through the exhaust. One riparian summarized the potential damage well: “The damage was devastating. Large sections of the carpeting were chewed up and nearly every wire he could get at was chewed on. The trolling motor is ruined and both transducer cables were chewed through. This all happened in one week as I was there the week prior.”

How to prevent muskrat damage? Michigan Lake and Stream Associations never condones violence toward aquatic animals, but it does recognize some animals can become a severe nuisance. There are several options that will prevent damage while leaving the muskrats unharmed. As many of their natural predators (coyotes, fox, eagles) have disappeared due to human development, their populations are often unnaturally high. One action that can at least reduce population pressure is to keep burrows away from your dock and boat. Muskrats are wary animals and will try to escape when threatened. When new burrows are discovered early on, the entry holes can be stuffed with rocks, balled-up window screen, and/or rags sprinkled with predator urine (mink, coyote, or bobcat—available from trapper supply outlets and over the Internet) or ammonia. Exposing their tunnels from above may also work. The success of this type of control depends on persistence from riparians and thus is often short-lived.

Another option it to install a muskrat guard on your boat. These installs in the exhaust and have threaded bars that can be adjusted to hold it firmly in place. At $245 to over $400, depending on the size of your exhaust, they’re pricey but a lot cheaper than replacing your boat. Note: many insurance policies typically exclude damage caused by “vermin,” which includes muskrats – riparians should check their coverage and consider working to getting muskrat damage covered if there is a problem in your area.

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